NaCl/ZnO/α-Al<sub>2</sub>O<sub>3</sub> 촉매상에서 메탄의 Oxidative Coupling의 속도론적 고찰

김상채; 서호준; 선우창신; 유의연

Journal of the Korean Industrial and Engineering Chemistry, Vol.3, No.2, 256-265, June, 1992

Export Citation

NaCl/ZnO/α-Al₂O₃ 촉매상에서 메탄의 Oxidative Coupling의 속도론적 고찰

Kinetics of Oxidative Coupling of Methane over NaCl/ZnO/α-Al₂O₃ Catalyst

김상채, 서호준, 선우창신, 유의연

초록

NaCl(30wt%)/ZnO(60wt%)/α-A1₂O₃ 촉매상에서 메탄의 oxidative coupling 반응의 속도식을 연구하여 활성 산소종에 관하여 고찰하였다. 반응온도 650℃에서 750℃까지 메탄의 전화율 10%미만의 범위에서 메탄과 산소의 분압을 변화시켜 가면서 메탄의 전환속도를 측정하여 속도식을 검증하였다. 제안된 메틸라디칼의 생성반응은 Langmuir-Hinshelwood형 반응기구를 따른다. 촉매표면의 서로 다른 활성점에 흡착된 메탄분자와 산소분자가 반응하여 메틸라디칼이 생성되는 반응이 속도결정단계이며, 이때 활성화 에너지는 약 39kca1/mo1이었다. 메탄의 C-H 결합의 해리에 관여하는 산소종은 표면상의 이원자 산소인 O₂^2-나 O₂^-로 제시할 수 있었다.

The kinetics for the oxidative coupling of methane over NaCl(30wt%) /ZnO(60wt%)/α-Al₂O₃ catalyst was investigated, and then the active oxygen species were discussed. The conversion rate of methane was measured at the atmospheric pressure with various combinations of partial pressure of methane and oxygen at temperature range of 650℃∼750℃, at conversions less than with 10%. These rate data were then used to verify the proposed Langmuir-Hinshelwood kinetic equation. The rate limiting step appeared to be the formation of the methyl radicals by the reactin of the adsorbed methane and the adsorbed oxygen, which were adsorbed on the different active sites of the catalyst. The activation energy of the methyl radical formation was estimated to be ca. 39 kcal/mol. From the kinetic studies, the oxygen species respolsible for the formation of methyl radicals was proposed to be diatomic oxygen such as O₂^2- or O₂^- on the surface.

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[1] Lee JS, J. Chem. Ind. Tech., 6(3), 88 (1988)

[2] Keller GE, Bhasin MM, J. Catal., 73, 9 (1982)

[3] Hinsen VW, Baerns M, Chem. Ztg., 107, 223 (1983)

[4] Ito T, Lunsford JH, Nature, 311, 721 (1985)

[5] Otsuka K, Liu Q, Hatano M, Morigawa A, Chem. Lett., 467 (1986)

[6] Sofranko JA, Leonard JJ, Jones CA, J. Catal., 103, 302 (1987)

[7] Lo MY, Agrawal SK, Marcelin G, J. Catal., 112, 168 (1988)

[8] Shepelev SS, Lone KG, J. Catal., 117, 362 (1989)

[9] Karf SJ, Roos JA, Derksen JWHC, Vreeman JA, Ommen JG, Ross JRH, Appl. Catal., 59, 291 (1990)

[10] Peng XD, Stair PC, J. Catal., 128, 264 (1991)

[11] Ito T, Wang JX, Lin CH, Lunsford JH, J. Am. Chem. Soc., 107, 5062 (1985)

[12] Peng XD, Richards DA, Stair PC, J. Catal., 121, 99 (1990)

[13] Lin CH, Campbell KD, Wang JX, Lunsford JH, J. Phys. Chem., 90, 534 (1986)

[14] Otsuka K, Jinno K, Inorg. Chim. Acta, 121, 237 (1986)

[15] Otsuka K, Murakami Y, Wada Y, Said AA, Morigawa A, J. Catal., 121, 122 (1990)

[16] Lin CH, Wang JX, Lunsford JH, J. Catal., 111, 302 (1988)

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[18] Mirro EE, Santamaria JM, Wolf EE, J. Catal., 124, 465 (1990)

[19] Kim SC, Ph.D. Dissertation, Chonnam National Univ., Kwang-ju (1991)

[20] Kim SC, Sunwoo CS, Yu EY, Korean J. Chem. Eng., 7(4), 279 (1990)

[21] Aika K, Lunsford JH, J. Phys. Chem., 81, 1393 (1977)

[22] Krylov OV, React. Kinet. Catal. Lett., 35, 315 (1987)

[23] Driscoll DJ, Martir W, Wang JX, Lunsford HH, J. Am. Chem. Soc., 107, 58 (1985)

[24] Lee JS, Oyama ST, Catal. Rev.-Sci. Eng., 30(2), 249 (1988)